In certain applications of pulsed laser radiation, a specific wavelength of radiation, characteristic of a certain type of laser, may be preferred, or may even be necessary. In such applications, the maximum average power in a pulse sequence from a single one of that type of laser may often be less than would be desirable for that application, for example for providing a desired manufacturing throughput. Maximum average power can be limited because the laser cannot generate sufficient energy per pulse, or cannot deliver pulses having sufficient energy at a sufficiently high pulse-repetition frequency (PRF).
One means of overcoming this limitation is to combine pulse sequences from two lasers, each capable of delivering pulses of sufficient energy for the application, interleaved in time at a site to be irradiated by the pulses. This can provide a combined pulse sequence having a PRF twice that of the individual lasers and, accordingly, twice the average power, and can effectively double the throughput of an application without providing an additional tool or delivery device for the pulses.
In an application requiring a high spatial precision for delivery of the pulses, for example, laser machining or laser marking, it would be important to have pulses from each laser arrive at precisely the same location on material being machined or marked. Accordingly, there is a need for apparatus for combining beams for two repetitively pulsed lasers that will temporally interleave pulses, and spatially combine the pulse sequences, precisely, along a common beam path.